This invention relates to cryptographic security techniques and, more particularly, to an arrangement for authenticating the identity of a terminal user provided with an identification number and a secret password.
Identifying numbers such as account numbers and identification cards such as charge cards and employee identification cards bearing the identification number of the person being identified have been used for some time as a means for accessing data bases. To the extent that the identification number and identification card can be secured from third parties, the identification card itself provides authenticating evidence tending to verify that the holder is the person authorized to access the data base. In view of the fact that a person's charge account number is often embossed on the identification card, however, and the fact that an identification card or credit card can easily be lost or copied, the evidentiary value of an identification card is quite limited. Supplemental evidence that the person who is presenting an identification card is the person authorized to hold the card and obtain access to the data base is often presented in the form of a memorized password or other authenticating information obtainable only from the authorized card holder, such as a digitized fingerprint, voice print, or dynamic signature analysis information. It is known in the prior art to encrypt the password or other authenticating information (either in a reversible or irreversible mode) and store the encrypted authenticating information in a data base accessible by the identification number for comparison with a password provided by a potential computer user.
A serious exposure of these known table look-up identity verification methods is that a hostile system programmer or computer operator may be able to interchange the encrypted authenticating information for his own account with that of the encrypted authenticating information for another's account and thereby gain access to the other person's account by giving his own password to the system. After gaining access to the other person's account, the encrypted authenticating information records could be returned to their authorized position to cover the tracks of the illicit transaction.
Another exposure of the simple table look-up methods of the prior art is that simple cryptographic functions are utilized. For example, the characteristic identifying information is encrypted for storage and decrypted for comparison with authenticating information submitted at a terminal. Alternately, the encrypted authenticating information may be stored and authenticating information encrypted at a terminal may be transmitted directly to the host computer for direct comparison. In either event, it is possible for hostile persons to create new accounts with associated passwords and obtain the encrypted form of the password at a terminal which will be stored in the data base table for later use in attacking a data base such as might be owned by a bank. Thus, the resources of the institution owning the computer would be exposed to attack as well as individual accounts or data sets within the data base as previously described.
Accordingly, it is an object of the invention to provide a secure method of authenticating the identity of a user of an information system.
Another object of the invention is to provide a secure method for protecting authentication information used to verify the identity of a potential user of an information system.
A further object of the invention is to provide authentication patterns at a host data processing system for the users of the system each being a cryptographic function of a user identification number and a secret password.
Still another object of the invention is to provide verification patterns at the host data processing system for the users of the system each being a cryptographic function of a predetermined number and the user identification number.
Still a further object of the invention is to provide a table of user test patterns at the host data processing system for the users of the system each being a cryptographic function of the corresponding user authentication pattern and verification pattern.
Still another object of the invention is to provide a table of user test patterns by an irreversible cryptographic function.
Still a further object of the invention is to provide user test patterns by a cryptographic function using a variant of the system master key.
Still another object of the invention is to provide a user authentication pattern at a terminal of the system which is a cryptographic function of the user identification number and a secret password.
Still a further object of the invention is to provide a first verification pattern at the host system which is a cryptographic function of a predetermined number and the user identification number provided at the terminal and transferred to the host system.
Still another object of the invention is to provide a second verification pattern at the host system which is a cryptographic function of the user authentication pattern provided at the terminal and transferred to the host system and the user test pattern accessed from the table of user test patterns.
Still a further object of the invention is to provide the second verification pattern by an irreversible cryptographic function.
Still another object of the invention is to provide the second verification pattern by a cryptographic function using a variant of the system master key.
A data communication system in accordance with the invention includes one or more terminals operatively coupled to a host data processing system each having cryptographic apparatus for cryptographic data communications. In order to authenticate the identity of terminal users of the system, a host system initialization process is first performed to provide a table of test patterns for use during subsequent authentication processing. This is accomplished by providing terminal user identification numbers and passwords and a predetermined number at the host data processing system. A first initialization operation is performed at the host data processing system in accordance with the terminal user identification numbers and passwords to obtain terminal user authentication patterns. A second initialization operation is performed at the host data processing system in accordance with the predetermined number and the terminal user identification numbers to obtain terminal user first verification patterns. A third initialization operation is performed at the host data processing system in accordance with the terminal user authentication patterns and the terminal user first verification patterns to obtain the table of terminal user test patterns.
During authentication processing, a terminal user identification number and password are provided by a user at a terminal of the system. An operation is performed at the terminal in accordance with the terminal user identification number and password to obtain a terminal user authentication pattern. The terminal user identification number and authentication pattern is then transferred to the host data processing system to carry out an authentication process. At the host data processing system, a first operation is performed in accordance with the predetermined number and the received terminal user identification number to obtain a terminal user first verification pattern. The table of terminal user test patterns is then accessed in accordance with the received terminal user identification number to provide the test pattern corresponding to the terminal user. A second operation is performed at the host data processing system in accordance with the accessed terminal user test pattern and terminal user authentication pattern to obtain a terminal user second verification pattern. The first verification pattern is then compared with the second verification pattern to authenticate the identity of the terminal user.
The foregoing and other objects, features and advantages of the invention will be apparent from the following particular description of the preferred embodiment of the invention, as illustrated in the accompanying drawings.